Pound split by Italian page for fussy fault-finder (3-6)

'fussy fault-finder' is the definition.
(someone finding faults in things)

'pound split by italian page' is the wordplay.
'pound' becomes 'nicker' (nicker can informally mean pound sterling).
'split by' is an insertion indicator.
'italian' becomes 'it' (abbreviation for Italian).
'page' becomes 'p'.
'it'+'p'='itp'
'nicker' going around 'itp' is 'NIT-PICKER'.

'for' acts as a link.